In well-known load transport equipment, each self-propelled truck is usually controlled for preventing a rear-end collision so that trucks do not collide with each other.
Therefore, in the well-known load transporting equipment, a photoelectric switch is provided at the front of each self-propelled truck travelling along a travel rail, the photoelectric switch being used to set a first detection region in front of the self-propelled truck, thereby enabling the existence of other self-propelled trucks in the detection region to be detected. Also, the front of each self-propelled truck is provided with a photosensor receiver for detecting the light emitted from the front, and the rear of the truck is provided with a photosensor transmitter which projects the light toward a second detection region extending farther from the first detection region set by the photoelectric switch and expanding wider than the first detection region.
When the photosensor receiver of a running rear truck receives the light from the photosensor transmitter of another self-propelled truck in front, the speed of the rear truck is reduced from high to lo. Also, when the photoelectric switch of a rear truck detects another self-propelled truck in front, the rear truck stops, thereby preventing a rear-end collision between both the trucks.
However, for the well-known load transporting equipment, the photosensor transmitter must spread the light to be transmitted so as to enable the light to be received even at a curved portion of the travelling rail. However, it has been impossible to project the light in the distance sufficiently to permit a reduction in speed in time to prevent a rear-end collision with the truck in front.